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Knight Msold <br /> Mr. Robert Emst, Geolo.-ist -2- Apri1 29, 1998 <br /> United States Department of the Interior <br /> in the leachate. High chloride levels and other concerns were addressed in a letter dated January <br /> 26, 1998 from Knight Piesold to the DMG. This letter was also forwarded to the BLM. In order <br /> to reduce chloride levels in the leachate, a more thorough rinsing procedure was developed for <br /> the pilot scale operation. Another sample of tailings material from the process with the new <br /> rinsing procedure was collected and analyzed using the SPLP test. The result of this analysis is O,,_� INS <br /> provided in Table 1. N� <br /> The SPLP test method is used to characterize waste material for its potential to release metals and <br /> other constituents into the environment due to exposure to normal meteoric precipitation. In this <br /> procedure a minimum of 100 grams of solid waste is combined with 20 times that weight of <br /> slightly acidic, artificial rain water. Traditionally, the U.S. EPA recommends that concentrations <br /> of constituents in the resulting leachate be compared with 100 times drinking water standards as <br /> an indication of the material's toxic characteristics. This rationale assumes that a 100-fold dilution <br /> occurs prior to use of the leachate mixture as a drinking water source and follows from the <br /> practice of comparing Toxic Characteristic Leaching Procedure (TCLP) results to Maximum <br /> Concentrations of Contaminants for Toxicity Characteristics (MCCTCs) which are equivalent to <br /> 100 times drinking water standards. <br /> Table 1 presents the results of the SPLP procedure and compares them to values equal to 100 <br /> times U.S. Primary and Secondary Drinking Water Standards (DWS), where available. None of <br /> the measured constituents from the tailings leachate exceeded the 100 times DWS values. <br /> We also compared the leachate results to the undiluted drinking water standards. Manganese, <br /> which has a secondary drinking water standard, is the only constituent to exceed its associated <br /> standard. Manganese in the leachate had a level of 0.321 mall in the leachate which is <br /> approximately six times the standard of 0.05 mg/I. <br /> To determine the probability of the manganese in the leachate affecting a drinking water source, <br /> we obtained a list of the nearest wells to the Joker Mine. According to the Colorado Division of <br /> Water Resources database, the nearest down-gradient well is approximately 5 miles from the site. L <br /> This well is listed as a domestic use well. Another domestic use well is approximately 1.5 miles <br /> east of the mine site but based on topographyis not down gradient from the mine. If leachate <br /> � g w� 'i; •i <br /> were to enter the ground water, by the time it reached the nearest well, manganese levels are ` S �',i <br /> expected to be undetectable. Five wells are on the Joker Mine property and their listed uses r <br /> include industrial and domestic. These wells are not likely to be used for sources of water but two \ <br /> it <br /> of the wells are being proposed as monitoring wells. <br /> The Elkhead Joint Venture proposes to monitor the ground water during operations. Quarterly <br /> monitoring of one up-gradient and one down-gradient well will be implemented. Ground water <br /> sampling of these wells will be conducted prior to backfilling the pit with tailings material to <br /> determine existing ground water quality. Monitoring will continue through the reclamation of the <br /> site. <br />